Alkylation of hydrocarbons



Dec. 1l, 1962 s. R. STILES ALKYLATION OF' HYDROCARBONS Filed June 5,1959 2 Sheets-Sheet l AGENT Dec. 11, 1962 s, R, s'rlLEs 3,068,308

ALKYLATION OF HYDRO-CARBONS Filed June 3, 1959 2 Sheets-Sheet 2 SAMUELR. STILES BY Uf anw AGENT 3,068,398 ALKYLATEN F HYDRCARRNS Samuel R.Stiles, Cressltili, NJ., assigner to The M. W. Kellogg Company, JerseyCity, NJ., a corporation of Delaware Filed `inne 3, i959, Ser.. No.817,799 7 Claims. (Cl. 26d-683.62)

This invention relates to an improved alliylation process and moreparticularly to the alkylation of isoparafiins with olens in thepresence of an alkylation catalyst to produce hydrocarbon compoundsboiling in the gasoline boiling range. In one aspect the inventionrelates to improving the efciency and economy of an alkylation process.In other aspect the invention relates to an improved method ofseparating products of an alkylation reaction.

Among the various catalytic processes which have made possible andeconomical the production of fuels having a quality rating of betterthan 90 octane for both automotive and aviation use, the alkylation ofhydrocarbons is of greatest importance. Of the various alkylationprocesses currently in use, for example, the alkylation of an oleiinwith an olefin, the alkylation of an aromatic compound with an olen andthe allo/lation of an isoparallin with an olen, the latter is by far theforemost in importance. Some reasons for this are: isoparafiins as wellas olens are converted, resulting in an increased product yield, thealkylate is essentially free from gumforming materials so that additivesare not required; the alkylate has a higher tetraethyl lead responsethan polymerized oleiins and the performance in super-charge engines issuperior to most other catalytically produced fuels.

Generally, the alkylation of an isoparailin with an olefin involvescontacting these reactants in the presence of a catalyst in analkylation zone, removing lower boiling hydrocarbons which enter thesystem in the reactant feed streams, removing the crude alkylate productand treating it to neutralize and remove sulfur-bearing contaminantswhich are sometimes formed in the reaction zone. The treated alkylate isthen deisoparainized and the isoparafn removed, usually as a vapor, iscondensed and recycled to the reaction zone while the deisoparaflinizedalltylate mixture is removed and treated tor further puriiication andseparation.

Many chemical and engineering problems are involved in the design andoperation of an eilicient alkylation process. The reaction between thealltyiatable hydrocarbon and oleiin in the presence of an alkylationcatalyst is exothermic and the heat of reaction must be removed duringthe reaction for maintenance of operating conditions. ln addition,diluents which enter the alkylation reactor in the feed thereto must beremoved from the system in order to avoid the accumulation andinterference in the rate of reaction and to maintain a relatively lowvolume of circulation. The temperature of the reaction is controlled andthe heat of reaction is removed from the alkylation reactor byvaporizing a portion of the isoparaiiin rich hydrocarbon. The lighterdiluents, being more volatile than the isoparain, are concentrated inthe vapors and can be removed from the reacting system by processingthese vapors.

Since it is known that the quality of the alkylate product is improvedby a high concentration of the alltylatable hydrocarbon with respect toolein in the alkylation zone during the reaction, the unreactedconstituent must be eticiently and economically separated from thevaporous diluent phase for return to the reaction zone and furtherreaction with olefin. In this way a desirable mol ratio of alkylatablehydrocarbon to olen is maintained. The

separation of alliylatable hydrocarbon from lower boiling material isaccomplished by means of distillation Zones wherein the lower boilinghydrocarbon diluents are successively concentrated in the vapor streams.Since a relatively large volume of material is passed to saiddistillation zones from said alkylation reactor, much expense and lossof ethciency has been incurred in this stage of the process.

it is, therefore, an object of this invention to provide an improvedprocess for the alkylation of hydrocarbons in the presence of analkylation catalyst.

it is another object of this invention to provide a more etiicient andeconomically feasible method of carrying out alkylation reactions.

Still another object of this invention is to provide an improved methodfor separating products of an alkylation reaction.

Still another object of this invention is to provide a more efricientand economical method of removing low boiling hydrocarbon diluents froman alitylation system.

Still another object of this invention is to increase the ratio ofallrylatable hydrocarbon with respect to olen in the reaction zone.

Another object of this invention is to decrease the volume of inerts inthe alkylation reacting system.

@ther objects and advantages of the present invention will becomeapparent to those skilled in the art from the following description anddisclosure.

According to the process of this invention, an ailiylatable hydrocarbonis reacted with an olefin in the presence of an alkylation catalyst inan allrylation contactor to produce a vaporous etlluent containingunreacted alkylatabie hydrocarbon and lower boiling hydrocarbons and aliquid effluent containing alkylate product. The vaporous ehluent isremoved from the contactor, condensed and passed to a flashing zonewherein a vaporous fraction and a liquid fraction are formed. At least aportion, and preferably all of the liquid fraction which containsconcentrated alkylatable hydrocarbon is directly recycled to theailtylation contacter as a part of the alkylatable hydrocarbon feedthereto, while the vaporous fraction, wherein lower boiling diluents areconcentrated, is condensed and passed to a distillation zone, togetherwith any of the liquid fraction not returned directly to the reactor. lnthe distillation zone, hydrocarbons boiling below the alkylatablehydrocarbon are removed as a vapor. The alkylatable hydrocarbon isremoved from the distillation zone as a liquid and is then recycled tothe alltylation contactor as a part of the feed thereto.

The liquid etiiuent withdrawn from the contactor is treated for theremoval of acid contaminants such as acid esters and the decontaminatedalltylate mixture which, in the preferred reaction of the presentinvention, contains isoparafn, n-parafn and alkylate product is furthertreated to separately recover one or more of the above constituents ofthe decontaminated alkylate mixture.

A novel method of separating the abovc-mentioned constituents of thealkylate mixture comprises passing the liquid to a fractionation zonefrom which the isoparaflin is removed as a vaporous overhead fraction,the n-parafn is removed as a vaporous side fraction and the alkylateproduct is removed as a liquid fraction from the bottom of thefractionation zone. Since the separation of the various constituents iscarried out in a single operation, this method provides for simplicationof the alkylation process with greater economy of operation.

In carrying out the above process, a pressure is maintained on thealkylation reaction at about the boiling point of the alkylatablehydrocarbon reactant at a predetermined temperature, so that the heat ofreaction results in the vaporization of the lower boiling hydrocarbonconstituents `and a portion of the alkylatable hydrocarbon.

spaanse "it n 29 In this way, the reaction temperature is controlled andmaintained constant by evaporative cooling and the vaporous effluentremoved from the contactor is regarded as auto-refrigerant.

The liquid alkylate mixture removed from the allrylation contactor canalso be treated for the removal of contaminants and the separate removalof lower boiling paraffins in separate Zones, after which, the alkylateproduct is recovered as a product of the process or may be furthertreated by fractionation into light `and heavy fractions for use inspecific applications, such as, for example, aviation gasoline.

The process of the present invention is applicable to all alkylationprocesses involving the reaction between an `alkylatable hydrocarbon andan oletin in the presence of a catalyst. However, the preferred processinvolves the reaction between an isoparafiin and an olefin in thepresence of a liquid acid catalyst. rThe isoparafns which may be usedinclude: isobutane, isopentane, isohexane, etc., or mixtures hereof andthe olefins reacted with these isoparafiins include: ethylene,propylene, butylene, pentylene, and oletinic isomers and dimers,trimers, tetramers and mixtures thereof. lt is also within the scope ofthis invention to utilize any proportion of the above as feed stocksand, in addition, mixtures of isoparafiins and olens in the presence orabsence of n-paramns.

A wide variety of catalysts are available for use in the alkylation ofan isoparaihn (an alkylatable hydrocarbon) with an olefin. Amon(T thecatalysts included within the scope of this invention are mineral acidssuch as sulfuric acid, hydrouoric acid, phosphoric acid, chlorosulfonicacid, fluo'r'osulfonic acid, etc., which may be used either singly or in'admixture Non-solid Friedel-Crafts catalysts which form a liquid phasesubstantially irnmiscible with the hydrocarbon phase may also beernployed. These include the conventional Friedel-Crafts metallichalides, such `as, aluminum chloride, in an acid such as those justenumerated and metallic halide-hydrocarbon complexes. Other liquidcatalyst which provide a heterogeneous reaction mixture with thealkylatable hydrocarbon may also be employed within the scope of thisinvention.

When alkylating van aromatic compound such as benzene with an olefin, orexample, ethylene or propylene, the reaction is carried out in thepresence of a catalyst such as those enumerated above. However, thepreferred catalysts include those of the Friedel-Crafts type andphosphoric acid or salts of phosphoric acid such as pyrophosphoric acid.The most preferred reaction of the present invention involves thereaction between isobutane and an olefin in the presence of a sulfuricacid or hydrofiuoric acid catalyst.

Generally, the allrylation reaction takes place over a wide range oftemperature and pressure, ranging from about -50 F. to about 500 F. andfrom about 0 p.s.i.g. to about 1000 p.s.i.g. However, the preferredreaction of the `presentinvention is preferably carried out at atemperature of between about 25 F. and about 100 F., `and a pressure offrom about 0 p.s.i.g. to about 100 p.s.i.g. To establish favorableconditions for the production of high octane alkylate in high yields, itis desirable to contact the reactants, in a plurality of zones, withvigorous agitation so as to provide uniform mixture of the reactantsland, to maintain `at the point of contact, a high concentration ofalkylatable hydrocarbon as compared to olefin. This can be accomplishedby introducing olefinic hydrocarbons into an emulsified stream ofalkylatable hydrocarbons and acid which is moving past the point ofolefin introduction tat a high or maximum velocity.

Isobutane in sulfuricV acid, for example, has a limited solubility andsince the reaction of isobutane with olefins takes place in the acidphase with the acid catalyzing the reaction, the diffusion rates ofisobutane passing from the hydrocarbon phase to the acid phase and intosolution in the -acid phase is controlling. In a similar manner, theIalkylate products pass out of the acid phase and d into the hydrocarbonphase; olefin solubility is extremely high in the acid and reactsdirectly with the acid. As a result of these factors, rapidrecirculation of emulsion past a point olen injection within thereactor, provides a specific unit volume of acid emulsion to olefins fora short period of time (di) and this Volume of emulsion is momentarilysaturated with olefin which reacts with the isobutane, thus decreasingthe isobutane availability. Recovery, or resaturation, of this volumewith isobutane is completed before this unit volume is recontacted witholefins. r[he time required depends on the diffusion rates. This factoris a basic factor in this type of liquid-liquid reaction system and isexpressed by the following correla- Vu V l Amp-'acera wherein,

Af is the quality factor of the alkylate resulting from conditionspresent in the acid phase listed below',

V is the volume of emulsion;

E is the acid concentration by volume of the emulsion;

O is the olefin feed rate in barrels per hour;

R is the emulsion recycle rate in barrels per second;

Cm is the system diffusion constant;

l is the isobutane concentration in the hydrocarbon phase;

and

A is the alkylate concentration in the hydrocarbon phase.

By the following expressions it is possible to calculate the spacevelocity and intervals at which olefin is injected into a given volumeof emulsion.

VE/O is equal to the space velocity in the reactor,

V/B is equal to the time between olefin injections into the emulsion.

in the operation of the present invention, the volume per volume ratioof isoparafn to acid is generally between about 2:1 and about 15:1 andthe ratio of isoparafn to olefin feed in a reaction zone falls withinthe range of from about 2:1 mols to about 150:1 mols in the reactor. Atthe point of Contact, the isoparaiiin to olefin ratio can be as high as1000: 1. Prior art processes have shown that mol ratios of up to about10:1 or less isoparaiiin to olefin are commonly used; however, by theprocess of the present invention, as hereinafter described, it ispossible to achieve a higher molar excess of akylatable hydrocarbon orisoparafiin in the alkylation zone resulting in a higher qualityalkylate product.

The major portion of the isoparafin present in the reactor is preferablyprovided by a recycle stream obtained from a subsequent distillationstep, namely, the deisoparaiiinization step, and from theauto-refrigerant stream as hereinafter described; although, a majorportion of isoparafn may be continuously supplied from an outsidesource, if desired. Normally, a portion of the isoparaiiin is introducedinto the contactor with the olefin reactant and a second portion isemulsilied with the catalyst prior to contact with olefin. However, itis also within the scope of this invention to introduce the entireisoparatfin charge with the catalyst.

it has been found that the formation of undesirable reaction by-products(esters) in the reaction zone is inversely proportional to the molarexcess of isoparaflin while the formation of higher quality alkylate isdirectly proportional to the molar excess of isoparaiin. Therefore, molratios of between about 20:1 and about 150:1 isoparalfn to olefin in thereactor are preferred. The higher mol ratios of this range are obtainedwhen operating the deisoparaffinization zone as a stripper and/ or bythe improvement of the present invention.

Although the present alkylation process is adaptable to any one of thenumerous types of contacting appara` tus employed for allo/lation andmay be carried out inl one or more stages, the preferred apparatus andmethod which is particularly suited to the present process,V is thecascade type reactor wherein the alkylatable hydrocarbon and acid areemulsiiied in each of several confined reaction zones in several stagesin series and the olefin is separately introduced and is uniformlydispersed throughout the emulsion in each reaction zone. The reactionmixture passes serially through the plurality of reaction zones withinthe reaction section of the contacter wherein the temperature ismaintained at a constant low level by vaporizing the lighter componentsof the reaction mixture including some of the isoparafn reactant. Thereaction mixture then enters a separation section wherein liquid andvapor phases are separated. ln the separation section, the liquidcatalyst, preferably an inorganic acid such as sulfuric acid, is alsoremoved from the liquid hydrocarbon phase and a portion of the acidseparated is generally recycled to the reaction section, usually afterbeing fortified with fresh acid so as to maintain the catalyst in ahighly concentrated state, for example, preferably above about 85percent sulfuric acid.

In the processof the present invention, the liquid hydrocarbon phasewhich, in the preferred process contains a mixture of isoparatfin,alkylate and acid esters, when sulfuric acid is employed as thecatalyst, and which may or may not contain normal butane and residualacid catalyst, can be treated to remove traces of catalyst and estercontaminants when they are present. The decontaminated alkylate mixtureis then passed to a first distillation zone or a deisoparamnization zonewherein the alkylatable hydrocarbon or isoparaftin is distilled from thealltylate mixture at a temperature between about 50 F. and about 375 F.under from about 0 p.s.i.g. to 200 psig., preferably in anisopara'hn-olen system at a tower bottoms temperature between about 50F. and about 250 l?. under a tower top pressure from about p.s.i.g. toabout 140 p.s.i.g. The concentrated alkylate can then be subjected tosubsequent reuernent steps such as the removal of n-paraiiins, ifpresent, and the fractionation into light and heavy alltylate fractions.The removal of acid and acid esters is accomplished by water-washing,bauxite treating, dilute caustic washing or combinations of these orother known treating steps, although the addition of caustic as aneutralizing agent followed by waterwashing at an elevated temperature,is usually preferred.

The vaporous effluent in the alkylation contactor usually contains someentrained liquid which, for practical purposes should be removed beforethe vapors are subjected to further treatment. A convenient andefficient method of removing this liquid comprises passing the vaporsthrough a coalescing device which, by impingement contact, removes theliquid and provides means for returning it to the liquid etfluent in thecontactor. It is to be understood, however, that any method of drying orremoving entrained liquid from the vaporous eiuent may be employed ifdesired without departing from the scope of this invention.

The treated vaporous efiiuent or auto-refrigerant is passed to acompressor wherein it is compressed to a pressure at which the vaporscan be condensed by heat eX- change with water or air or other coolingmedia, to between about atmospheric pressure and about 175 psig., butusually to a pressure in excess of that employed in the reaction zone.The compressed vapors are then removed frorn the compressor and at leastpartially condensed. In the case of an isoparafn-oletin alhylationsystem, the vapors are preferably compressed to 1cetween aboutatmospheric pressure and about 150 psig., whereas in an aromatic-olefinalkylation, the vaporous etiiuent is preferably compressed to betweenabout atmospheric and about 30 p.s.i.g. In certain instances, forexample, where the alkylation reaction is carried out at temperaturesabove the available cooling media temperature, compression can beavoided and the vaporous eliluent can be directly condensed with coolingmedia.

At least a major portion of the vapors are condensed;

however, it is preferable to totally condense the vaporous effluentafter compression, when compression is employed. The resulting condensedeiuent together with any of the remaining vapor is then subjected to aflashing operation to produce a liquid alkylatable hydrocarbon phase anda vaporous phase, which contains the low boiling diluents or inertmaterials which enter the reaction Zone in the feed materials. Thevaporous phase is then withdrawn, condensed and passed to a seconddistillation zone for removal of low boiling components from the system.'fhe flashing operation serves to concentrate the low boiling materialsin the vaporous phase and to produce an alkylatable hydrocarbon liquidphase which is substantially free of the low boiling diluents. Thus, theliquid phase can be directly and continuously recycled to thealizylation zone, thereby increasing the excess of alkylatablehydrocarbon available for further reaction with oleiin in the zone. yBythis method of operation, important process and economic advantages ofthe present process are realized.

The flashing zone can also be used in indirect heat exchange withalkylatable hydrocarbon recycle or olefin feed or both to cool thesefeeds prior to entry into the alkylation reactor. When employed as aheat exchanger, the flashing zone can also be employed to condense thevaporous overhead from the subsequent distillation zone, if desired.

Generally, the temperature and pressure conditions employed in theflashing zone are dependent upon the boiling points of the low boilingmaterials which are to be removed from the system and which form thevaporous phase in the dashing zone when an isoparain-olein alkylationsystem is under consideration, a temperature of `between about 25 F. andabout 110 F. and a pressure P of from about 30 p.s.i.g. to about 150p.s.i.g. is preferably employed. However, it is to be understood thathigher or lower temperatures or pressures may be used in accordance withthe particular demands imposed by the nature of the materials undergoingseparation The vaporous phase, which also contains some alkylatablehydrocarbon, is condensed or compr-essed and con` densed and passed to asecond distillation zone for the removal of low boiling diluents as avapor from the system. The expansion which takes place in the dashingzone considerably reduces the pressure at which the resulting vapors arewithdrawn and since the subsequent second distillation is generallycarried out at a higher pressure, the vapor from the flashing zone ispreferably compressed to a pressure consistent with that required in thefollowing distillation. By operating in this manner, the seconddistillation Zone is greatly reduced in size (number of trays) orfractionation load (liquid-vapor loading) since a relatively smallvolume of material is treated therein.

The alkylatable hydrocarbon which remains as a liquid in the seconddistillation zone is Wi hdrawn and recycled to the alkylation contactoras a part of the feed thereto.

When the second distillation zone is operated at a higher temperaturethan the temperature employed in the contactor, the liquid from thedistillation zone is first cooled and then recycled. The cooling can beaccomplished in many Ways, one of which includes auto-refrigerativechilling or flash chilling which is a preferred modification of thepresent invention. This technique involves passing the liquid from thesecond distillation zone to a second flashing zone, compressing andcondensing the vaporous portron and admixing the condensed portion withincoming liquid. The resulting liquid portion can then be recycled tothe contactor.

In the present process, Where isobutane is employed as the alkylatablehydrocarbon, the following conditions are most preferred. The alkylationreaction is carried out at a temperature of between about 0 F. and about70 F. under from about atmospheric to about 30 p.s.i.g. The vaporousefliuent from the contactor is compressed to from about 50 p.s.i.g. toabout 150 p.s.i.g. at a. condensaaosaeos tion temperature-of about y50F. and about 130 F. The vapor is then condensedand flashed at atemperature between about 45 F. and about 110 F. under from about 20p.s.i.g. to about 100p.s.i.g.-\and the vaporous phase from theashingzone is-distilled at between about 190 F.- and about 230 F. under fromabout 200` p.s.i.g. to about 270 p.s.i.g.

For a better understanding of the present invention, reference is nowhad to the accompanying drawings, Fi@- URES 1 and 2. FIGURE lillustrates the improvement in the treatment of the auto-refrigerant bywhich the advantages of the present invention are obtianed. in this.

embodiment an isoparailin, such as isobutane, is fed into contactor 3from line 2 and is reacted with an olen, such as butylene, enteringcontactor 3 from lines 4, 4ta), 4(b),. 4(0) and 4(d). The reaction iscarried out at a temperature of between about 30 F. and about 70 F.,under from about 5 p.s.i.g. to about 30 p.s.i.g. in the presence f1anacid catalyst, for example, sulfuric acid of at least 85 percentconcentration entering the contactor together with isoparan in line 2.Generally, the isoparatiin and the liquid catalyst are emulsied prior tocontact with olen thus providing more favorable reaction conditions andreducingthe formation of undesirable lay-products toa minimum. Theisoparafn-acid emulsion is reacted with the olefin by passing theemulsion serially through a plurality of reaction zones with separateintroduction of olen into each zone. During the reaction, low boilinghydrocarbons and some of the isoparaftin reactant vaporizes to form avaporous effluent. The vaporous effluent and the unvaporized liquidefuent which contains n-paraiiin, isoparain, alkylate, acid catalyst andacid contaminants, arepassed to a separation section of contacter 3wherein the -vaporous and liquid effluents are separated. The vaporouseffluent is withdrawn from lthe separation section by means of conduit6.

The liquid eilluent is then separated into liquid acid `catalyst and aliquid hydrocarbon mixture or alkylate mixture. The acid catalyst iswithdrawn from the con- -tactor by conduit and a portion of the acid isremoved from `the system for regeneration by means of line while freshacid is supplied to line 5 from line S to maintain a concentration ofacid at least 85 percent.

The vaporous ellluent removed from the contactor in line 6 enters thesuction of compressor dd, is compressed #to a pressure of from about yp.s.i.g. to about 150 p.s.i.g. at a .condensation temperature of betweenabout 50 F. and about 130 F. The resulting compressed vapor which isdischarged from the compressor through con- ;duit 6, Vis passed to watercooler 52 wherein it is condensed by lindirect heat exchange with waterand the condensate and any uncondensed vapors are passed to flashingzone 56. In hashing zone 56, the liquid is expanded and a pressure belowthe compression pressure and above the ,pressure in the contacter, i.e.,from about 50 p.s.i.g. to about .100.p.s,i.g. at a correspondingcondensation temperature of between about F. and about 110 F., ismaintained onthe condensate in this zone. Under these conditions avaporous portion, rich in low boiling materials, and a liquidportion ofconcentrated isoparafin is produced.

`The liquid portion is withdrawn from zone 56 and recycled to .thealkylation contactor by means of conduits 58.and.2, whereas the Vaporousportion is withdrawn by line 62 from Vzone 56, compressed in compressor60 to a pressure not in excess of 300` p.s.i.g. and condensed incooler64 so that it can be pumped to holding drum ed thence todistillation zone 70 by means of the line o3. Any Tentrained vapor isvented from drum 66 by means of vent .72.

. The liquid in line dit is pumped to distillation zone 70 wherein lowboiling diluents are separated from liquid isoparam. -The distillationzone is operated with redux to the top of the zone in order to maintaindistillation lconditions and continuous separation of hydrocarbonsboiling beiow the isoparaiiin reactant. This distillation zone ismaintained at a temperature of between about 50 F. and about 250 F.under from about 50 p.s.i.g. to about 300 psig. Under these conditions,materials boiling below the isoparain reactant, are removed from zone 70m^d the system, as a vapor, in line 7d; whereas the reining liquid,which is predominately isoparain, is withdrawn from zone 70 and passedin indirect heat exnge by line T76 with the iiquid alkylation mixture inexchanger Ire as hereinafter described. The cooled radin fromdistillation zone 70, in line 76, is n finder cooled to about thetemperature at which the ylation reaction takes place by subjecting theliquid to auto-refrigerative cooling in flashing zone '7S which isprovided with refrierative cooling by withdrawing vapors linecompressing the vapors in compressor S2, condensing tl^ vapors in cooler34 and returning the cooled liquid to o '76 entering dashing zone '73.The liquid from hing zone 7S is then returned to the alkylationcontacter as a part of the feed thereto by means of conduit and 2.

The liquid hydrocarbon mixture or alkylate mixture is withdrawn from thecontactor by means of line l0 and passed to coalescer il?. for removalof entrained acid. The clarified liquid is then heated by indirect heatexchange ywith a recycle stream in line 24 and heat exchanger 14,

hereinafter described, and then in heat exchanger 16 by pumping theliquid mixture through line 17. After heating, the liquid is passed fromline li to neutralization "ore wherein the liquid neutralized withcaustic is y hed with water at an elevated temperature to remove acidiccontaminants such as sulfate esters. The neutralized liquid is thenpassed from line i9 to distillation zone, or-deisoparatiinization zone,20, wherein the alkylatable hydrocarbon or isoparain is separated fromthe liquid Aalltylate mixture as a vaporous fraction in line 24. Makeupisoparailin feed to supply needed reacting equilibrium of isoparah'inand oleiin, is also introduced into the deisoparahinization zone fromline 22. ln the particular embodiment shown in the drawing, zone 20 isoperated as a stripper, however, it is to be understood that one is notprecluded from using a conventional reilux deisobutanization zone, ifdesired.

i'eboiling of the deisoparanization zone is maintained by an externalreboiler line in indirect heat exchange with steam or other heatingmedia and the deisoparainization is carried out at a temperature ofbetween about 50 F. and about 375 F. under from about 0 p.s.i.g. toabout 200 psig.

The vaporous isoparaiiin fraction is then condensed in condenser 25 andthe resulting liquid is passed from conduit Zd through theaforementioned indirect heat exchanger .td in indirect heat exchangewith the liquid alkylate mixture. Thereby the liquid is further cooledand recycled to the alkylation contactor as a part of the feed theretoby means of lines 241 and 2.

The deisoparafnized alkylate mixture from zone 20 is pumped by means ofline 26 to deparainization zone wherein n-paraiiin is removed from theliquid alkylate at a temperature of between about F. and about 380 F.under from about 20 psig. to about 90 p.s.i.g. The distillationconditions in zone 28 are maintained by a reboiler in indirect heatexchange with steam or other heating media. Redux is supplied to the topof zone 28 by withdrawing vaporous n-paralin in line 30, condensing thevapors in cooler 32 and recycling a portion of the n-parain from holdingdrum 34- to the top of tower 28. Theremaining portion of liquid n-paranis withdrawn from the system by means of line 36 as a product of theprocess.

Liquid alkylate is removed from the bottom of zone and pumped by meansof line 3S to rerun tower 40 om which light alkylate product isrecovered from line and a lower boiling heavy alkylate product isrecovered from line 4d. Reiiux is supplied to tower 40 -by line 42,condenser 4E and holding drum 50 while the tower is rela-oiled byindirect heat exchange with steam or other heating media. Thetemperature and pressure conditions employed in tower 40 depend uponmaterial undergoing fractionation and the particular desired boilingranges of the fractions to be separated. Generally, the temperature andpressure employed in an isopararnn-olen system are withm the range ofbetween about 100 F. and about 450 F. and from 5 p.s.i.g. to about 25p.s.i.g.

Referring now to rlGURE 2 of the drawing, wherein the novel treatment ofauto-refrigerative vapors is combined with the novel method ofseparating products from the liquid alkylation mixture, it is noted thatthe modication of this drawing entails many of the process stepsdiscussed above for FlGURE. 1. Isoparar'lin in line 102 is introducedinto alkylation reactor' 103 together with t'ortiiied acid catalyst fromline 104 and these constituents are emulsiiied and contacted with oleiinreactant entering the contactor from lines 10.5, 10501), 105(b), 105(c)and 150(d). The reaction is carried out in a plurality of zonesindicated in the drawing by various olefin feed lines and the reactiontakes place in a manner identical with that set forth in FIGURE 1.Generally, vapors formed in each zone of the contactor are withdrawnfrom unit 103 by vapor take-off lines (not shown) and returned to theseparation section of the unit for nnal withdrawal through line 106after liquid entrained therewith has been removed, preferably by meansof a coalescing device, (not shown). The liquid effluent is separated,in the separation section, into a liquid acid phase and a liquidalkylate mixture. The liquid acid phase is withdrawn from contactor 103,a portion thereof is removed from the system for regeneration throughline 107 and the remaining portion of the acid, after being fortifiedwith fresh acid from line S to maintain a desirable concentration, isrecycled to the reaction section of contactor 103.

The vaporous etlluent in line 1116 containing diluents which enter thesystem in the reactant feeds is passed to compressor 154 and compressedto a pressure of from about 50 p.s.i.g. and about 150 p.s.i.g., afterwhich the vapors are condensed in condenser 152 and thereafter pumped tohashing zone 156. In flashing zone 156, the liquid is expanded to form aliquid phase and a vaporous phase and the liquid phase withdrawn fromashing Zone 156 by means of line 15S and recycled to contactor 103 bymeans of line 102 as part of the isoparaiiin feed thereto. The vaporousfraction in flashing zone 156 wherein the diluents or materials boilingbelow the alkylatable hydrocarbon are concentrated, are withdrawn fromthe llashing zone by conduit 162, compressed in compressor 163, andcondensed in coo-ler 164 after which the condensate is pumped to holdingdrum 1de. The vapors which are at a pressure of between about 50p.s.i.g. and about 100 p.s.i.g. and a temperature of between about 25 F.and about 110 F. in flashing zone 156 are c0mpressed to a pressure notin excess of abo-ut 300 p.s.i.g. and the condensed vapors are passed toholding drum 166. The condensate is then withdrawn from holding drum 1&6by means of conduit 163 and pumped to reuxed distillation zone 170wherein the above-described low boiling materials are removed as avaporous fraction in line 174` from the remaining liquid isoparalfinfraction. The liquid material, which is withdrawn from zone 170 in line176, is then passed through indirect heat exchanger 116 in indirect heatexchange with the liquid alkylate mixture, as hereinafter described, andthe cooled liquid from distillation zone 170 is withdrawn from heatexchanger 116 by line 176 and passed to flashing zone 178 wherein theliquid is further cooled by auto-refrigerative chilling. This liquid iscooled to approximately the temperature employed in the allcylationcontactor by removing the vaporous fraction from flashing zone 178 inline 180, compressing the vapor in compressor 182, condensing the vaporin cooler 184 and then admixing the result- 10 ing condensate withliquid entering the flashing zone through line 176. The liquid fractionfrom ilashing zone 178 is then recycled to the contactor by means oflines 106 and 102 as part of the isoparaffin feed thereto.

rThe liquid alkylate mixture is withdrawn from contactor 103 throughline 110 and is passed to separator 112 for further removal of residualacid catalyst and other acid material which may be entrained therewith.The acid removed from separator 112 can be recycled to the alkylationcontactor in line 104- or can be preferably passed to acid withdrawalline 107, if desired. The liquid alkylate mixture is withdrawn fromseparator 112 by means of line 117 and pumped through indirect heatexchanger 114 in indirect heat exchange with recycle isoparaflin,hereinafter described. The liquid mixture is further heated by pumpingit to heat exchanger 116 in indirect heat exchange with liquid in line176 described above. After emerging from heat exchanger 116, the heatedliquid alkylate mixture is passed to neutralization zone 118 wherein itis washed with water at a temperature of between about 140 F. and about175 F. for removal of acid ester contaminants from the liquid alkylatemixture. Caustic is added to the water as needed to neutralize acid oracidic material extracted to prevent corrosion. The decontaminatedliquid alkylate mixture is then withdrawn from the neutralization zoneby line 119 and passed to fractionation zone 120 wherein the variouscomponents in the alkylate mixture are fractionated and separatelyrecovered. For example, when the mixture comprises alltylate, isoparafhnand n-paralin, a temperature and pressure of between about 50 F. andabout 160 F. and from about 15 p.s.i.g. to about 145 p.s.i.g. ismaintained in the top of the tower; a temperature of between about 60 F.and about 185 F. and a pressure of from about 20 p.s.i.g. to about 150p.s.i.g. is maintained in the middle portion of the tower and atemperature of between about 180 F. and about 355 F. and a pressure offrom about 25 p.s.i.g. to about 155 p.s.i.g. is maintained in the bottomof the tower. When the alkylate mixture contains allrylate, isobutaneand n-butane, the following are representative set of conditions: towertop at 140 F. under 105 psig.; mid tower at 165 F. under 110 psig.; andtower bottom at 300 F. under psig. Heat is supplied to tower 120 by eansof at least one reboiler, in FlGURE 2 reboiler line 123, which passesthrough indirect heat exchanger or reboiler 130 in indirect heatexchange with steam entering reboiler 130 by line 132. lt is to beunderstood, however, that other heat exchange media may be used in placeof steam, if so desired. Fresh isoparaiiin feed required to maintain thedesired reacting equilibrium of isoparain in the contactor is alsopumped into tower 120 by means of line 122 and vaporous isoparaliin iswithdrawn from the top of tower 1Z0 through conduit 124 and condensed incondenser 125; vaporous n-paran is withdrawn from the middle portion ofthe tower through line 134, condensed in cooler 136 and recovered as aproduct of the process and liquid alltylate product is recovered fromtower 120 by line 126. The liquid alltylate product can be subjected tofurther treatment such as separation into fractions having certainspecific boiling points, if desired or required, for particularapplications. The liquid n-parafn product can be further puriiied orsent to disposal, if desired.

The liquid isoparafn fraction in conduit 124 is then further cooled bypassing said vapors through indirect heat exchanger 114 in indirect heatexchange with the liquid alkylate mixture, hereinabove described, andthe resulting liquid isoparaffin is recycled to contactor 103 by meansof lines 124 and 102. as a part of the isoparaliin feed thereto.

The following examples are oered as a better understanding of thepresent invention and are not to be construed as unnecessarily limitingto the scope thereof.

1E t. ll The examples are carried out according to the teachings of thespecification and the vdrawings described above.

Example 1 In a cascade alkylation reactor, a continuous stream ofsulfuric acid of about 98 percent concentration and isobutane containingabout percent n-butane and a smaller amount of lower boilinghydrocarbons such as propane, is introduced in a mol ratio of about 1:7acid to isobutane. The isobutane mixture and sulfuric acid catalyst areemulsied, flashed, to initially remove low boiling materials prior tothe reaction and the resulting emulsion is passed to a confined reactionzone wherein it is contacted with butylene in a mol ratio of about :1,isobutanezbutylene.

The reaction between isobutane and butylene to form alkylate having ahigh octane rating takes place at about F. under about 6.7 p.s.i.g. in aplurality of confined reaction zones through which the emulsion ispassed. in each zone the emulsion, under vigorous agitation induced by amechanical mixer, is contacted with butylene which is separatelyintroduced into each zone. During the course of reaction, materialsboiling below the isoparaffin and a portion of the isoparafn arevaporized and withdrawn from the reaction Zone in order to control thereaction temperature. After the reaction is completed, these vapors,together with the resulting liquid reaction product mixture, is passedto a separation zone wherein the vapors, comprising isobutane and lowboiling hydrocarbons such as .propane and methane are separated from theliquid phase containing isobutane, n-butane, alkylate product, sulfuricacid catalyst and small amounts of acid esters. The vapors are passedthrough a coalescing device which serves to remove any liquid entrainedtherein and return the liquid to the liquid Vreaction product mixture.The liquid product mixture is then passed through a wire coalescer toseparate liquid acid from the liquid hydrocarbons and the coalescedliquid is allowed to settle. The acid which separates from thehydrocarbons is withdrawn and a. portion thereof is fortified to about a98 percent concentration with fresh acid and recycled to the reactionzone. The hydrocarbon liquid or alkylate product mixture is withdrawnfrom the reactor and is passed through a second coalescer to furtherseparate entrained acid and sulfur-bearing impurities therefrom. Theseparated acid and impurities are then removed from the system forpurification.

The liquid alkylate mixture is'then treated in a twostage water-wash ata temperature of about 140 F. under about 150 p.s.i.g. Caustic is addedto neutralize acid released and to prevent corrosion. The liquid is thenpassed to a coalescing device wherein water and neutralized acidiccontaminants such as sulfate esters are removed from the liquid alkylatemixture.

The decontaminated liquid alliylate mixture is then pumped to adeisobutanization Zone which is operated at a bottom temperature ofabout 240 F. under about 105 p.s.i.g. The temperature is maintained atthe bottom of the deisobutanization tower by means of steam heatedreboilers. A vaporous isobutane fraction is removed from the top `of thedeisobutanization zone at a temperature of about 140 F., the Yvapor iscondensed and the isobutane condensate is passed in indirect heatexchange with the liquid allrylate mixture emerging from said secondcoalescer to further cool said condensed isobutane. The isobutanecondensate, which is cooled to about the reaction temperature in thecontactor, is then directly recycled to the reaction section of thealkylation contactor to maintain the high concentration of isobutane inthe reaction zone.

The liquid alkylate product removed from the lower portion of thedeisobutanization Zone is then passed to a debutanization tower which isoperated at a bottom temperature of about 300 F. under about 75 p.s.i.g.by means of a steam reboiler. A vaporous n-butane fraction is removedfrom the top of the debutanization tower and is condensed, a portionbeing employed as reux to said kan tower and the remaining portion beingwithdrawn as a `product of the process. VLiquid alkylate product is re-Separated as a vapor from a liquid fraction boiling above .thesetemperatures. The vaporous fraction is condensed and recovered as avproduct of the process suitable for use as an aviationgasoline whilethe liquid is recovered as a heavyalkylate product of the processsuitable for use in blending automotive fuel. Of the material passed tothe rerun tower percent is considered as light alkylate having an octanenumber of at least 97.5.

The vaporous er'iiuent, or auto-refrigerant removed from the alhylationcontactor at a temperature of about 35 F. under about 6 p.s.i.g. is thencompressed to about 97 p.s.i.g. and a corresponding temperature of about160 F. lThe resulting compressed vapors are then condensed by indirectheat exchange with water at F., and dashed at a temperature at about 60F. under about 30 p.s.i.g. to produce a vaporous phase and a liquidphase. The liquid phase is then recycled to the alkylation reaction zoneat the temperature and pressure required in the contacter and aids inmaintaining the high isoparaffln to olefin ratio (25:1) in the reactionZone.

The vaporous phase is reco-mpressed to a pressure of about p.s.i.g. anda corresponding temperature of F. and the resulting compressed vaporsare condensed at a temperature of about 105 F., after which, thecondensate is pumped to a depropanization Zone operated at F. underabout 250 p.s.i.g. A vaporous overhead fraction comprising propane andmethane is withdrawn from the depropanization zone and from the system.The remaining liquid is withdrawn from the lower portion of thedepropanization zone, cooled to a temperature of about 35 F. by passingthe liquid in indirect heat exchange with the liquid alkylate mixtureleaving said second coalescer and by further chilling in anauto-refrigeration zone. The resulting cooled liquid is then recycled tothe alkylation reaction zone as a part of the isobutane feed thereto.

Example 2 The reaction set forth in Example 1 between isobutane andbutylene in the presence of sulfuric acid and the treatment of thevaporous reactor eiuent was repeated under substantially the sameconditions of temperature, pressure and mol ratios. The procedure forrecycling spent acid and coalescing and water-washing the liquidalkylate mixture at an elevated temperature was also repeated undersubstantially the same conditions set forth above. However, thedecontaminated liquid alkylate mixture withdrawn from the watercoalescer is passed, in the present example, to a fractionation Zonewhich is operated at a bottom temperature of about 345 F. under 120p.s.i.g. and a tower top temperature of about 142 F. under about 105p.s.i.g.

A'vaporous isobutane fraction is removed from the top of thefractionation zone at atemperature of about 140 F. under 100 p.s.i.g.These vapors are then condensed by heat exchange with water and theresulting liquid passed in indirect heat exchange with the liquidalkylate mixture leaving said second coalescer to further cool theliquid isobutane fraction, and recycled to the alkylation reaction Zoneafter emulsifying with the sulfuric acid catalyst.

Another vaporous fraction is withdrawn from the middle portion of thefractionation tower at a temperature of about 167 F. under about 110p.s.i.g. This vaporous fraction, which comprises essentially n-butane,is condensed and recovered as a product of the process. The liquidbottoms fraction, which is the alkylate product, is withdrawnV atatemperature of about 300 F. or slightly above, under 115 p.s.i.g. Aportion of this liquid is recovered as a product of the process whilethe remains,oes,sos

ing liquid portion is passed in indirect heat exchange with steam andrecycled to said fractionation zone to maintain the bottom temperaturetherein. A very high grade alkylate product having an octane number ofabout 98 is recovered as the product of the process.

The invention as described herein relates to an improved method formaintaining a high excess of alkylatable hydrocarbon in an alkylationreaction zone by withdrawing a vaporous efliuent from said zone,condensing the vaporous etiiuent and flashing the condensate and anyvapors entrained therewith, to concentrate low boiling materials in avaporous phase and alkylatable hydrocarbon, which is suitable for directrecycle to the reaction zone, in a liquid phase. The invention alsorelates to an improved method for separating products of an alkylationreaction which comprises the aforementioned treatment of the vaporouseiiiuent and the treatment of the liquid alkylate mixture in a singlefractionation zone from which isoparaiiin, n-paraflin and alkylateproduct are separately removed at various points of the fractionationzone which is maintained at different temperature levels. The componentswhich are separately removed from the fractionation zone are immediatelyrecoverable as products of the process.

Although the above-described improvements relate particularly to thealkylation of an isoparaffin with an olefin in the presence of a liquidcatalyst, it is to be understood that other types of alkylationreactions, such as the alkylation of benzene with an olefin such aspropene and the alkylation of other aromatics are contemplated withinthe scope of this invention.

Having thus described my invention, I claim:

1. In an alkylation process which comprises reacting an isoparaflin withan olefin in the presence of a sulfuric acid catalyst at a temperatureof between about 25 F. and about 100 F. under from about 0 p.s.i.g. toabout 100 p.s.i.g. in a multi-zone alkylation contactor to producetherein a vaporous fraction free of sulfuric acid and sulfate estercontaminants and containing unreacted isoparaffin and a lower boilinghydrocarbon and a liquid fraction containing alkylate product, unreactedisoparaffin and acidic contaminants; separating the vaporous isoparaffinand lower boiling hydrocarbon fraction from the liquid fraction;separating the sulfuric acid catalyst from the liquid fraction; andrecovering alkylate product from the treated liquid fraction as aproduct of the process; the improvement which comprises: compressing thevaporous fraction to a pressure between about 14.6 p.s.i.g. and about175 p.s.i.g.; condensing the compressed vaporous fraction; passingsubstantially all of said condenn sate to a flashing zone to separatesaid condensate into a liquid phase consisting essentially ofisoparaflin and a vaporous phase more concentrated in lower boilingmaterials; recycling the liquid phase to the alkylation contactor as apart of the reaction feed thereto to maintain a high molar excess ofisoparaiiin therein; condensing the vaporous phase to produce a secondcondensate; distilling substantially all of the second condensate in adistillation Zone to remove hydrocarbon boiling below said isoparafn asa Vapor from the resulting second liquid isoparaliin phase; employingthe second liquid isoparatiin phase as a heat exchange medium to heatsaid liquid fraction prior to subsequent refinement and to cool saidsecond liquid isoparaffin phase to a ternperature of between about 25 F.and about 100 F. under from about p.s.i.g. to about 100 p.s.i.g.; andrecycling said second liquid isoparafn phase to said contactor as a partof the feed thereto at substantially the same conditions of temperatureand pressure employed in the contactor.

2. The process of claim l wherein the isoparafiin is isobutane.

3. The process claim 1 wherein the olefin is butylene.

4. In an alkylation process which comprises reacting isobutane with anolen in the presence of sulfuric acid at a temperature of between about25 F. and about 1007 F. under from about 0 p.s.i.g. to about 100p.s.i.g. in a multi-zone akylation contactor to produce therein avaporous fraction free of sulfuric acid and sulfate ester contaminantsand containing unreacted isobutane and a lower boiling hydrocarbon and aliquid fraction containing alkylate product, unreacted isobutane andacidic contaminants; separating the vaporous isobutane and lower boilinghydrocarbon fraction from the liquid fraction; separating sulfuric acidfrom the liquid fraction; and recovering alkylate product from thetreated liquid fraction as a product of the process; the improvementwhich comprises: compressing the vaporous fraction to a pressure ofbetween about 14.6 p.s.i.g. and about 150 psig.; condensing thecompressed vaporous fraction and passing substantially all of saidcondensate to a flashing zone maintained at a temperature of betweenabout 25 F. and about F. under from about 30 p.s.i..g. to about 100psig. to separate said condensate into a liquid phase consistingessentially of isobutane and a vaporous phase more concentrated inhydrocarbons boiling below sai-d isobutane; recycling the liquid phaseto the alkylation contactor as a part of the reaction feed thereto atsubstantially the same temperature and pressure as employed in saidcontactor to maintain a high molar excess of isoparain therein;condensing the vaporous phase to produce a second condensate; distillingthe entire second condensate in a distillation zone at a temperature ofbetween about 50 F. and about 250 F. under a pressure of from about 50p.s.i.g. to about 300 p.s.i.g. to remove hydrocarbon boiling below saidisobutane as a vapor from the resulting second liquid isobutane phase;employing the second liquid isobutane phase as a heat exchange medium inindirect heat exchange with said liquid fraction prior to the refinementof said liquid fraction; and recycling the resulting cooled secondliquid isobutane phase to said contactor as a part of the feed theretoat substantially the same conditions of temperature and pressureemployed in the contactor.

5. The process of claim 4 wherein the treated liquid effluent from thecontactor is distilled to remove isobutane as a vaporous fraction fromthe liquid alkylate; the compressed condensate in said flashing zone isiiashed in indirect heat exchange with said vaporous fraction; and thevaporous fraction is recycled to the contactor as isobutane feedtogether with the liquid phase from said flashing zone.

6. ln an alkylation process wherein an isopararlin is reacted with anolefin in the presence of sulfuric acid as a catalyst in a multi-zonecontactor under conditions such that only isoparaffin and lower boilingmaterials are vaporized to provide a vaporous eliiuent free of sulfuricacid and sulfate ester contaminants and a liquid effluent containingalkylate product, acidic contaminants, and unreacted isoparafiin, thevaporous isoparaiiin and lower boiling hydrocarbon efliuent is separatedfrom the liquid eftiuent and condensed and the alkylate is recoveredfrom the liquid eiuent as a product of the process, the improvementwhich comprises: iiashing the entire isoparaffin and lower boilinghydrocarbon condensate to separate said condensate into a concentratedisoparafiin liquid phase and a vaporous phase more concentrated in lowerboiling hydrocarbon; recycling the concentrated isoparaf lin liquidphase to the contactor as a part of the reactant feed thereto tomaintain a high molar excess of isoparafiin therein; condensing thevaporous phase to produce a second condensate; distilling the entiresecond condensate to remove hydrocarbon boiling below said isoparalin asa vapor from the resulting second liquid phase thus concentrated inisoparaiin; passing said second liquid phase in indirect heat exchangewith the liquid effluent containing alkylate to aid in the heatrequirements of further purification of the alkylate in the liquidetlluent; and recycling said second liquid phase thus cooled to saidcontactor as apart of the feed thereto.

7. lnvan alkylation process which comprises reacting isobutane withbutylene in the presence of sulfuric acid as a catalyst at a temperatureof between about 25 F. and about 100 F. under from about psig. to about10() p.s.i.g. in a multi-zone alkylation contacter, to produce therein avaporous fraction substantially free of sulfuric acid and sulfate estercontaminants and containing unreacted isobutane and a lower boilinghydrocarbon and a liquid fraction containing alkylate product, unreactedisobutane, n-butane, and acidic contaminants; separating the vaporousisobutane and lower boiling hydrocarbon fraction from the liquidfraction and separating the sulfuric acid catalyst from theremainingliquid hydrocarbon mixture to produce a liquid alkylatemixture; the improvement which comprises: compressing said separatedvaporous fraction to a pressure o from about 50 p.s.i.g. to about 15()p.s.i.g.; condensing said compressed vaporous traction; 'passingsubstantially all of said condensate to a flashiufy zone to separatesaid condensate into a liquid phase consisting essentially of isobutaneand a vaporous phase more concentrated in hydrocarbon boiling below saidisobutaue, at a temperature of between about 45 F. and about 110 F.under from about 20 p.s.i.g. to about `1GO psig.; recycling the liquidphase to the allcylation contacter as a part of the feedthereto, atsubstantially the same temperature and pressure employed in saidcontacter; compressing said Vaporous phase Vto a pressure of betweenabout 200 p.s.i.g. to about 270 psig.; condensing said compressedvaporous phase to produce a second condensate; distilling said secondcondensate in a distillation zone at a temperature of between about 190F. and about 230l F. under a pressure of from about 20() p.s.i.g. toabout 27() p.s.i.g. to remove hydrocarbon boiling below said isobutaneas a vapor from the resulting second liquid isobutane phase;decompressing said second liquid isobutane phase; employing said secondliquid isobutane phase as a heat exchange medium in indirect heatexchange with said liquid alkylate mixture to heat said mixture prior tosubsequent reiineirent thereof; and recycling said second liquidisobutane phase to said contactor as a part of the feed thereto atsubstantially the same temperature and pressure employed in saidcontacter.

References Cited in the ile of this patent UNITED STATES PATENTS OTHERREFERENCES Goldsby et al.: The Gil and Gas Journal, vol. 54, No. 20,pages l04-7, September 19, 1955.

1. IN AN ALKYLATION PROCESS WHICH COMPRISES REACTING AN ISOPARAFFIN WITHAN OLEFIN IN THE PRESENCE OF A SULFURIC ACID CATALYST AT A TEMPERATUREOF BETWEEN ABOUT 25*F. AND ABOUT 100*F. UNDER FROM ABOUT 0 P.S.I.G. TOABOUT 100 P.S.I.G. IN A MULTI-ZONE ALKYLATION CONTACTOR TO PRODUCETHEREIN A VAPOROUS FRACTION FREE OF SULFURIC ACID AND SULFATE ESTERCONTAMINANTS AND CONTAINING UNREACTED ISOPARAFFIN AND A LOWER BOILINGHYDROCARBON AND A LIQUID FRACTION CONTAINING ALKYLATE PRODUCT, UNREACTEDISOPARAF-